Contactless bell



May 10, 1938. M. F. KETAY CONTACTLESS BELL Original Filed Feb. l2; 19322 Sheets-Sheet l .a INVINTOR Marr/5 CX/@Zay ATTORNEY May 10, 1938. M. F.KETAY CONTACTLES'S BELL Original Filed Feb. l2, 1932 2 Sheets-Sheet 2INVENTOR Y Mon/lsf/(etay ATTORNEY Patented May 10, 1938 UNITED sTATEsPATENT OFFICE coN'rAc'rLEss BELL Application February 12, 1932, SerialNo. 592,607

Renewed Juno 21. 1937 3Claims.

such as buzzers and/or bells, and more particularly to devices of thistype adapted to operate on alternating current without the use of make-5 and-break contacts.

Heretofore, devices of the above character adapted for either direct oralternating current energization, included a solenoid arranged toattract an armature upon energization of the former, and contacts whichwere broken upon attraction of said amature, thereby de-energizing thesolenoid and releasing the armature. This cycle was repeated as long ascurrent was supplied to the device to produce a continuous vibration ofthe armature. 'I'hese devices, a1- though suitable in installationswhere low voltages and relatively small currents are used, andrelatively small armatures are set into vibration,

are not suitable where higher voltages, such as standard commercialvoltages are used, because the breaking of the contacts to produce thevibrations of the armature, causes heavy arcing between the contactsthereby burning up and destroying the latter in a relatively short time.Accordingly, one of the objects of the present invention is to provide anovel buzzer or bell wherein make-and-break contacts are eliminated.

Another object of the invention is to provide a novel device of theclass described whereby the use of permanent magnets is unnecessary.

Another object is to provide a novel buzzer or bell which is adapted tooperate on alternating current of any desired frequency.

Another object is to provide a novel device of the above type which isadapted to operate on alternating current and the vibrating element ofwhich may be adjusted to operate at any desired frequency regardless ofthe frequency of the valternating current from which the device isenergized.

A further object of. the invention is to provide an alternating currentbuzer or bell which depends for its operation upon the theory 'ofresonance of an alternating current circuit 'whereby the device may betuned to operate at any desired frequency of the alternating currentsupply.

A still further object is to provide a novel construction of analternating current buzzer or bell whereby the frequency of the armaturemay be easily and quickly adjusted to any desired frequency and tooperate at the selected frequency independently of the frequency of thealternating current supply.

The above and other objects `and advantages (Cl. F15-335) The presentinvention relates to signal devices' of the invention will appear morefully hereinafter from a consideration of the detailed description whichfollows, taken together with the accompanying drawings, wherein isillustrated one form of the device embodying the present 5 invention. Itis to be expressly understood, however, that the drawings are for thepurpose of illustration and description only, and are not designed as adefinition of the limits of the invention. 10

In the drawings, wherein lik'e reference characters refer to like partsthroughout the several views,

Fig. 1 is a plan view, with the cover removed, of one form of the deviceembodying the present l5 invention;

Fig. 2 is a detailed sectional view taken on line 2-2 of Fig. l, of aconnection to the armature for operating the striker or clapper of a30tlg; 20

Fig. 3 is an inverted side elevation as viewed from the bottom of Fig.1;.

Fig. 4 isa graphical representation of the operational characteristicsof the device;

Fig. 5 is a, side elevation, partly in section, with 25 the coverattached; and- Fig. 6 is a plan view as viewed from the top of Fig. 5.

In accordance with the invention, the armature or vibrating member ofthe device is set 30 into vibration due to electro-magnetic attractionthereof by a coil or pair of coils energized by an alternating currentwhich increases and decreases as the resonance of a circuit includingsaid coil or coils and a capacity element is 35 approached and departedfrom by the action of the vibrating member.

Referring now to the drawings. and more particularly to Figs. 1 and 5,the device, in the form shown, comprises a base on which the vari- 40ous elements are mounted and having projecting ears 8, each of which isprovided with an aperture 5 for the reception of screws i0 so that acover Il may be secured to the base 1, as indicated in Figs. 5 and 6.Upon the base l, there is 45 mounted in any suitable manner, as by meansof screws I2 and il, a U-shaped laminated soft iron core Il, having legsor pole pieces I5 and i6. The pole pieces l5 and I6 are provided withend protecting members Il and i8, respectively, 50 of suitablenon-ferrous material for preventing the freezing" or sticking of thevibrating member to the legs or poles i5 and I6. A tuned circuit is nowprovided including inductance and capacity elements either of which maybe varied 56 so that the circuit may be periodically rendered resonantand non-resonant. The inductance elements comprise a pair of coils I9and 2l wound upon the legs I5 and I6, respectively, of the core I4 andarranged to be energized from a suitable source of alternating current(not shown) by means of the leads 2i and 22, which connect the coils toterminals or binding posts 23 and 24, respectively. The terminals 2l and24 are carried by a terminal block 25, of suitable insulating materialsecured to `the base "i in any suitable manner as by means of screws 28.Cooperating with and adapted to be at tracted by the pole pieces IIS andI6 upon energization ci' coils i9 and 20 for varying the impedance cfthe latter is an armature 21 consisting of soft iron laminations and issecured to a swivel rod 28 in any suitable manner, as by means of aclamp plate 29 and a screw $0.

The swivel rod 2B is provided for operating the striker or clapper of agong, as will be pointed out more fully hereinafter. but may bedispensed with in the event that the device is to be employed only as abuzzer, in which event the armature 21 may be pivoted to the base "l inany other suitable manner.

The armature l is normally held away from the pole pieces by means of acoil spring ll having dii one end thereof secured to the clamp plate 28and the other end to an adjusting screw I2 carried by a bracket 3Ssecured to the base 1. In this position of the armature the inductivereactancel of the coils is equal to capacitive reactance of the capacityelement and the circuit including said coils and capacity elements is atresonance. The spring 3i holds the armature 21 against a stop 34 whichmay be adjusted by means of a screw 35 carried by a bracket 3B securedto the terminal block 2b, so that the distanceof the amature from thepole pieces I5 and It may be adjusted for a purpose which will beapparent hereinafter, The capacity element of the tuned circuitcomprises a .condenser 31 mounted on a 'bracket 38 secured to the base 1in any suitable manner, as by means of screws 39 and 40, and connectedin series with the coils I! and 2li. The tuned circuli'l may be designedfor any suitable frequency.

It will be apparent thatfor a given frequency of the supply line fromwhich the device is energized, and with the armature 21 inthe openposition shown in- Fig. 1, the tuned circuit including the condenser 21and the coils I9 and 2l will be at resonance, as pointed out above, whenthe inductive reactance of the coils is equal to the Acapacitivereactance of the condenser, and at such time a maximum current will flowthrough the coils thereby attracting the armature 21. However, upon theattraction of the armature 21 the impedance oi' the coils is immediatelygreatly increased by virtue of the change or reduction of the air gapbetween the pole pieces and the armature, thereby throwing the circuitout of resonance, and so offering an extremely high impedance to theilow of current' in the coils Il and 20. Upon the decrease of current insaid coils the magnetic field of the pole pieces Il and Il is decreased,whereby the spring Il then pullsthe armature 21 away from the polepieces and the circuit is again restored to resonance, therebyincreasing the current flow through the coils and again attracting theamature 21, which in turn again reduces the'current ilow inthe coils andthe cycle of operation thusgoes on continuously so that the armature 27is set into vibration.

The operation will be more clearlyy apparent from the graphicalrepresentation shown in Fig. 4, which represents a resonance curveplotted in terms ofthe distance of the air gap between the armature andcoils as the abscissae and the current in the coils as the ordinates.The current is represented as i and is a maximum when the armature 21 ispositioned from the pole pieces Iland I a distance as. Therefore, itwill be seen that as the distance between the armature and the polepieces is decreased, which happens when the armature is attracted by thepole pieces and moved against said pole pieces so that the distance ofthe air gap is zero, the current in the coils will be a minimum, thisminimum being indicated my the point im.

The frequency of vibration of the armature 21 is entirely independent ofthe frequency of the current flowing through the coils I9 and-20 anddepends solely upon the tension of the spring 3| and to a slight extentuponthe distance that the armature has to travel between the stop 24 andthe pole pieces due to its inertia. The tension of the spring 3| must beovercome by the magnetic attraction of the armature by the pole pieces.Therefore the frequency of vibration of the armature may be readilychanged by turning the adjusting screw 32 to vary the tension on thespring 3l.

The resonance point of the circuit including the coils I9 and 20 and thecondenser 31 will of course be changed when an alternating currenthaving a different frequency is employed and, therefore, novel means areprovided whereby the circuit may be easily adjusted to resonance at thenew frequency by adjusting the initial distance 3 of the armature 21from the pole pieces lil and I6 and in the form shown said meanscomprise the adjusting screw 3B which moves the stop 34 further from orcloser' to the pole pieces. 'I'he adjustment of the stop 34, and hencethe distance lci? the armature 21 from the pole pieces, in effect tunesthe circuit because the changing of the air gap changes the impedance ofthe coils. It will therefore be seen that the device may be adjusted sothat the armature 21 can vibrate at any frequency independent of thefrequency of the alternating current, and the device may also beadjusted to operate effectively from an alternatlng current of anyfrequency, since the energizing circuit may be tuned to resonance at anyfrequency.

'Ihus far, the invention described constitutes a device generally knownas a buzzer, and may be used as such, but in the present embodiment, thearmature has been arranged to operate the striker or clapper of a bell.For this purpose the swivel rod 28 is journaled in bearings 4I and 42and extends through the base 1 and is provided with an extension 42 atright angles thereto, upon which is secured a striking ball 44 which,when actuated, strikes the bell or gong 45, the latter being secured tothe base 1 by the support 46. From the latter arrangement it will beseen that when the amsature 21 is vibrated, it will in turn rock theswivel rod 2l in its bearings. thereby imparting y an oscillating motionto the striking arm 43 which carries the ball 44 so that the latterrings the gong.

There is thus provided a novel buzzer or bell adapted to beoperated fromalternating current, which is relatively simple in construction andarrangement of parts, andin which permanent magnets and electricalcontacts are eliminated, thereby prolbnging the life of the device,since none of the working parts are susceptible to deterioration byburning due to arcing, which is generally produced in devices employingcontacts.

Novel means are also provided for adjusting the device so that it canoperate on an alternating current supply having any frequency, and meansare also provided whereby the frequency of vibration of the armature ofthe device may be adjusted to any desired value, which value isindependent of the frequency of the alternating current supply.

Although only one embodiment of the invention has been illustrated anddescribed, other changes and modiiications, which will now appear tothose skilled in the art, may be made without departing from the scopeof the invention, as for example, any other suitable means might beemployed for adjusting the frequency of vibration of the armature andfor tuning the device so that it may be adapted to operate onalternating currents of dinerent frequencies. Reference is therefore tobe had to the appended claims for a definition ofthe limits of theinvention.

What is claimed is:

1. A signal device including a core, a pair of coils wound on said core,an armature associated with said coils for attraction by the latter and.forming a closed magnetic circuit with the core when attracted by thecoils whereby the reactance of said coils is varied, an alternatingcurrent circuit including said coils and a condenser whereby saidcircuit is tuned to a predetermined frequency, said circuit beingresonant when the armature isaway from the coils and the magneticcircuit of the core is open thereby causing a relatively large currentto now through said coils and causing the latter to attract saidarmature whereupon the circuit is rendered non-resonant andthe currentin said`coiis decreaaed. means for pulling said amature away from thecoils to lopen the magnetic circuit of the core when the circuit isnon-resonant whereby resonance is again established and the armature setintofgvibration, means for adjusting the position of the armature withrespect to'the coils to establish the resonance point of the circuit inrelation to the frequency of the current employed to energize saidcoils, and means for adjusting the frequency of vibrationA of thearmature to any desired value independent of the frequencysooftheclrcuit.

2. A signal device comprising a core, a pair of coils wound on saidcore, an armature associated with said coils for attraction by thelatter and forming a closed magnetic circuit with the core whenattracted by the coils whereby the reactance of said coils is varied, analternating current circuit including said vcoils and a condenserwhereby said circuit is tuned to apredetermined frequency, said circuitbeing resonant when the armature is away from the coils and the magneticcircuit vof the core is open, thereby causing a relatively largecurrentto flow through said coils and causing the latter to attract saidarmature whereupon the alternating current circuit `is rendered.non-resonant and the current in said coflls decreased, means for pullingsaid armature away from the coils `toopen the magnetic circuit of thecore when the alternating current circuit is non-resonant wherebyresonance is again established and the armature set into vibration, andmeans for adjusting the position of the armature with respect to thecoils to establish the resonance point of the alternating currentcircuit in relation to the frequency of the current employedto energizesaid coils.

3. A signal device comprising a core, a winding on said core, anarmature associated with said core for attraction by the latter andforming a closed magnetic' circuit with the core whereby the reactanceorf said winding is'varied, an alternating current circuit includingsaid winding and a condenser whereby said circuit is tuned to apredetermined frequency, said circuit being resonant when the armatureis away from the core and the magnetic circuit of the core is openthereby causing a relatively large current to flow through said windingand causing the core to attract said armature whereupon the alternatingcurrent circuit is rendered non-resonant and the current .in saidwinding decreased, means for pullingsaid amature away from the core toopen the magnetic circuit thereof when the alternating current circuitis non-resonant whereby resonance 'isagain established and the amatureset into vibration, and means for adjusting the position of the armaturewith respect to the core Ito establish the resonance point of thealternating ciment circuit in relation tc the lfrequency of the currentemployed to energize said winding.

